warum kein kaffee vor blutabnahme — can a microbiome test help?

The instruction to avoid coffee before a blood draw is based on standard medical practice: caffeine can interfere with many lab values, including blood glucose, insulin, cortisol, catecholamines, and even liver enzymes. Even decaffeinated coffee may affect results due to other compounds. A microbiome test (e.g., stool analysis) cannot address this specific question, as it characterizes gut flora, not the acute metabolic effects of caffeine. Microbiome tests are designed for other purposes (e.g., digestive issues, inflammation markers) but not as a substitute for pre-analytical standards. Drinking coffee before a blood draw risks skewed results – regardless of your microbiome. The evidence here is established clinical practice, not a novel finding from microbiome research. Therefore: avoid coffee before blood tests; a microbiome test does not help with this.